Presently, most display devices support a discharge function. That is, when the power is turned off, an operating voltage of a display device will gradually decrease, and when the operating voltage is lower than a preset voltage, a clock signal input to a shift register will be pulled up to a first potential so that the shift register generates scan signals according to the clock signal which has been pulled up to the first potential to turn on a switching element in a pixel, which completely releases charges in the pixel, and thus avoids a long-term existence of the charge, which may result in residual image, flickering, and so on.